Porous carbon material, method for preparing the same, electrode comprising the same, and lithium-sulfur battery

Abstract

A porous carbon material, a method for preparing the same, a positive electrode including the same, and a lithium-sulfur battery including the same are provided. The porous carbon material has a specific surface area of 200 to 1,700 m 2 /g and impurities therefrom are removed through pre-treatment using microwaves. The porous carbon material, when applied to the positive electrode of the lithium-sulfur battery, improves the charging overvoltage problem of the lithium-sulfur battery.

1 . A porous carbon material with a specific surface area of 200 to 1,700 m 2 /g, from which impurities were removed through pre-treatment using microwaves. 
     
     
         2 . The porous carbon material according to  claim 1 , wherein, during the pre-treatment using the microwaves, the microwaves are applied to the porous carbon material under a condition that MPPT according to the following Equation 1 is 2,000 to 10,000 W·s/g:
   MPPT (W·s/g)=Microwave Power(W)×Time(s)/Weight of carbon material (g)  [Equation 1]
 
 wherein Time is a period of time in seconds during which the microwaves are applied, and is longer than 10 seconds. 
 
     
     
         3 . The porous carbon material according to  claim 2 , wherein the porous carbon material is selected from the group consisting of carbon nanotubes; graphene which is a multilayer graphene flake, MGF; graphite; carbon black selected from the group consisting of carbon black, acetylene black, Ketjen black, Denka black, thermal black, channel black, furnace black and lamp black; carbon fiber; and a mixture containing two or more thereof. 
     
     
         4 . The porous carbon material according to  claim 3 , wherein the porous carbon material is selected from the group consisting of carbon nanotubes, graphene, carbon black and Ketjen black. 
     
     
         5 . The porous carbon material according to  claim 1 , wherein a pore volume of the porous carbon material is 1.5 cm 3 /g or more. 
     
     
         6 . The porous carbon material according to  claim 1 , from which 90 to 100% of the total impurities contained therein have been removed. 
     
     
         7 . The porous carbon material according to  claim 6 , from which 99 to 100% of the total impurities contained therein have been removed. 
     
     
         8 . The porous carbon material according to  claim 1 , wherein the impurities comprise moisture and functional groups present in an inside and on a surface of the porous carbon material. 
     
     
         9 . A method for preparing a porous carbon material from which impurities have been removed, the method comprising:
 (a) putting a porous carbon material having a specific surface area of 200 to 1,700 m 2 /g into an airtight container, and then purging the airtight container with an inert gas by injecting the inert gas; and   (b) applying microwaves to the porous carbon material.   
     
     
         10 . The method according to  claim 9 , wherein, in step (b), the microwaves are applied to the porous carbon material under a condition that MPPT according to the following Equation 1 is 2,000 to 10,000 W·s/g:
   MPPT(W·s/g)=Microwave Power(W)×Time(s)/Weight of carbon material(g)  [Equation 1]
 
 wherein Time is a period of time in seconds during which the microwaves are applied, and is longer than 10 seconds. 
 
     
     
         11 . A positive electrode for a lithium-sulfur battery, the positive electrode comprising a sulfur-carbon composite in which sulfur is supported in the porous carbon material of  claim 1  as a positive electrode active material. 
     
     
         12 . The positive electrode according to  claim 11 , wherein there is no error in a content of sulfur and carbon material contained in the positive electrode active material. 
     
     
         13 . A lithium-sulfur battery comprising the positive electrode of  claim 11 ; a negative electrode; a separator between the positive electrode and the negative electrode; and an electrolyte comprising a first solvent containing a fluorine-based ether compound, a second solvent containing a glyme-based compound, and a lithium salt. 
     
     
         14 . The lithium-sulfur battery according to  claim 13 , wherein a utilization rate of sulfur contained in the positive electrode is 90% or more of the theoretical discharging capacity. 
     
     
         15 . The lithium-sulfur battery according to  claim 13 , wherein an energy density of the lithium-sulfur battery is 400 Wh/kg or more or 600 Wh/L or more.